package com.frame.compiler.utils;

import android.util.Base64;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.Cipher;

public class RSAUtil {
    public static final String CHARSET = "UTF-8";
    public static final String RSA_ALGORITHM = "RSA";
    /** 加密填充方式*/
    public static final String ECB_PKCS1_PADDING = "RSA/ECB/PKCS1Padding";

    public static Map<String, String> createKeys(int keySize){
        //为RSA算法创建一个KeyPairGenerator对象
        KeyPairGenerator kpg;
        try{
            kpg = KeyPairGenerator.getInstance(RSA_ALGORITHM);
        }catch(NoSuchAlgorithmException e){
            throw new IllegalArgumentException("No such algorithm-->[" + RSA_ALGORITHM + "]");
        }
        //初始化KeyPairGenerator对象,密钥长度
        kpg.initialize(keySize);
        //生成密匙对
        KeyPair keyPair = kpg.generateKeyPair();
        //得到公钥
        Key publicKey = keyPair.getPublic();
        String publicKeyStr = Base64.encodeToString(publicKey.getEncoded(), Base64.DEFAULT);
        //得到私钥
        Key privateKey = keyPair.getPrivate();
        String privateKeyStr = Base64.encodeToString(privateKey.getEncoded(), Base64.DEFAULT);
        Map<String, String> keyPairMap = new HashMap<String, String>();
        keyPairMap.put("publicKey", publicKeyStr);
        keyPairMap.put("privateKey", privateKeyStr);

        return keyPairMap;
    }

    /**
     * 得到公钥
     * @param publicKey 密钥字符串（经过base64编码）
     * @throws Exception
     */
    public static RSAPublicKey getPublicKey(String publicKey)  {
    	try {
    		//通过X509编码的Key指令获得公钥对象
            KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);

            X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(Base64.decode(publicKey, Base64.DEFAULT));
            RSAPublicKey key = (RSAPublicKey) keyFactory.generatePublic(x509KeySpec);
            return key;
		} catch (Exception e) {
            LogUtils.e("RSAUtil","获取公钥失败>>>"+e);
		}
        return null;
    }

    /**
     * 得到私钥
     * @param privateKey 密钥字符串（经过base64编码）
     * @throws Exception
     */
    public static RSAPrivateKey getPrivateKey(String privateKey){
    	try {
    		//通过PKCS#8编码的Key指令获得私钥对象
            KeyFactory keyFactory = KeyFactory.getInstance(RSA_ALGORITHM);
            PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decode(privateKey, Base64.DEFAULT));
            RSAPrivateKey key = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
            return key;
		} catch (Exception e) {
            LogUtils.e("RSAUtil","获取私钥失败>>>"+e);
		}
        return null;
    }

    /**
     * 公钥加密
     * @param data
     * @param publicKey
     * @return
     */
    public static String publicEncrypt(String data, RSAPublicKey publicKey){
        try{
            Cipher cipher = Cipher.getInstance(ECB_PKCS1_PADDING);
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            return Base64.encodeToString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), publicKey.getModulus().bitLength()), Base64.DEFAULT);
        }catch(Exception e){
            throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
        }
    }

    /**
     * 私钥解密
     * @param data
     * @param privateKey
     * @return
     */

    public static String privateDecrypt(String data, RSAPrivateKey privateKey){
        try{
            Cipher cipher = Cipher.getInstance(ECB_PKCS1_PADDING);
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
            return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decode(data, Base64.DEFAULT), privateKey.getModulus().bitLength()), CHARSET);
        }catch(Exception e){
            throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
        }
    }

    /**
     * 私钥加密
     * @param data
     * @param privateKey
     * @return
     */

    public static String privateEncrypt(String data, RSAPrivateKey privateKey){
        try{
            Cipher cipher = Cipher.getInstance(ECB_PKCS1_PADDING);
            cipher.init(Cipher.ENCRYPT_MODE, privateKey);
            return Base64.encodeToString(rsaSplitCodec(cipher, Cipher.ENCRYPT_MODE, data.getBytes(CHARSET), privateKey.getModulus().bitLength()), Base64.NO_WRAP);
        }catch(Exception e){
            throw new RuntimeException("加密字符串[" + data + "]时遇到异常", e);
        }
    }

    /**
     * 公钥解密
     * @param data
     * @param publicKey
     * @return
     */
    public static String publicDecrypt(String data, RSAPublicKey publicKey){
        try{
            Cipher cipher = Cipher.getInstance(ECB_PKCS1_PADDING);
            cipher.init(Cipher.DECRYPT_MODE, publicKey);
            return new String(rsaSplitCodec(cipher, Cipher.DECRYPT_MODE, Base64.decode(data, Base64.DEFAULT), publicKey.getModulus().bitLength()), CHARSET);
        }catch(Exception e){
            throw new RuntimeException("解密字符串[" + data + "]时遇到异常", e);
        }
    }

    private static byte[] rsaSplitCodec(Cipher cipher, int opmode, byte[] datas, int keySize){
        int maxBlock = 0;
        if(opmode == Cipher.DECRYPT_MODE){
            maxBlock = keySize / 8;
        }else{
            maxBlock = keySize / 8 - 11;
        }
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] buff;
        int i = 0;
        try{
            while(datas.length > offSet){
                if(datas.length-offSet > maxBlock){
                    buff = cipher.doFinal(datas, offSet, maxBlock);
                }else{
                    buff = cipher.doFinal(datas, offSet, datas.length-offSet);
                }
                out.write(buff, 0, buff.length);
                i++;
                offSet = i * maxBlock;
            }
        }catch(Exception e){
            throw new RuntimeException("加解密阀值为["+maxBlock+"]的数据时发生异常", e);
        }
        byte[] resultDatas = out.toByteArray();
        safeClose(out);
        return resultDatas;
    }

    public static void safeClose(OutputStream outputStream) {
        if (outputStream != null) {
            try {
                outputStream.close();
            } catch (IOException e) {
            }
        }
    }
}
